Correction method and intelligent vehicle guidance system for a composite-navigation of a motor vehicle

ABSTRACT

A correction method is provided for a map-supported navigation system or for a navigation system, in which the position of a motor vehicle found by means of composite navigation is checked and corrected. To correct the fed back position, a range of error is initially established, whose magnitude is determined by the tolerances of the vehicle sensors of the measuring errors of a navigation system. Within this range of error, all paved roads are taken into consideration as a possible vehicle position. A main route on which the vehicle is travelling is selected for the most probable position of the motor vehicle. The other positions continue to be used as parallel routes. If plausibility considerations reveal that a parallel route has a greater probability for the vehicle position than the present main route, then the parallel route is defined as the new main route. With the aid of a hysteresis, the current (actual) vehicle position is prevented from continually jumping back and forth among several streets.

FIELD OF THE INVENTION

The present invention relates to a method for correctingcomposite-navigation and to a navigation system of a motor vehicle.

BACKGROUND INFORMATION

When working with a map-supported navigation system, conventionalsystems are used to determine position using a composite-navigationprocess in which the data supplied by the sensors of a motor vehicle arecompared to those of a digital road map. The vehicle position determinedby the composite-navigation process is corrected, the vehicle beingplaced on a street that runs nearby. However, if many streets run at asimilar angle relative to the travel direction of the vehicle, it ispossible that the vehicle may be positioned on the wrong street. As itcontinues its trip, the vehicle remains on this "incorrect street",since no other test is performed to check the accuracy of thispositional correction.

European Patent Application No. 0 314 806 describes that a range oferror is determined for the estimated vehicle position, whose magnitudeis predetermined by the tolerances of the sensors for the length oftravel and the driving direction. By means of a computer, those vehiclepositions, which are transmitted for a given driving situation, arecalculated for all streets within the range of error. By estimating thedistances and other parameters, the vehicle position whose streetcharacteristic curve comes the closest is determined to be the actualposition. In this conventional method, the problem arises that whenworking with a narrow network of streets having several parallel routessituated closely together, the street can not always be found on whichthe vehicle is actually driving.

SUMMARY OF THE INVENTION

One of the advantages of the correction method and the navigation systemaccording to the present invention is that several possible vehiclepositions are calculated concurrently, all travel routes within adriving area being considered. Even when a main route is found for themost probable vehicle position, it is retained only until a parallelroute reaches a greater level of probability for the vehicle position onthe basis of plausibility considerations. This yields the advantage thatthe navigation vehicle guidance) becomes more reliable, and the vehicleis always localized on the street where it is actually located.

It is also advantageous to include the measuring tolerances of thesensors and/or of the navigation device, so that the range of error isalways calculated (or estimated) to ensure that the vehicle is situatedwithin the ranges of error. This ensures that the potential vehiclelocations are determined for all streets in the driving area.

It is also beneficial to select a street as the main route whosedirection substantially conforms with that of the composite navigationtravel route and which is the closest to the route. If the main route isselected again when additional measurements are taken, for example, alsoin view of the life span of the route or its angle of inclination, thenit is highly probable that it corresponds to the actual travel path ofthe vehicle.

To avoid vacillating back and forth to determine the most likely vehicleposition (main route position), for example, when streets run inparallel and at a small distance from one another in sections, anevaluation (qualification) hysteresis is provided, so that the mainroute is not changed until several measurements have proven such achange to be plausible.

When the length of the travel path is measured, sensor-related errorsoccur, which can then be simply recognized when the vehicle travels outor turns off at an intersection. Since the position of the intersectionis determined by its exact coordinates, a reference point is thusobtained between two measuring marks, which can be used to correct thelength measurement.

Since the position of the vehicle can also be determined usingnavigation satellites, the simplest way to eliminate errors occurringtransversely to the driving direction (route and direction) is tomathematically place the vehicle transversely to the driving directionon all roughly parallel running streets. These parallel routes arepursued further during continued travel and checked so that, after aplausibility check, the most probable parallel route is determined asthe new main route.

In addition, it is advantageous that when the present invention isemployed in a guidance system, the route is searched by using the mainroute as the starting point for a route calculation. Also, should therebe ambiguity with respect to the route (two or more routes nearlyequally plausible), the target (destination) route can become thecriterion for deciding the main route selection, since the probabilityis great that the driver of the vehicle will follow the routerecommended by the system. Using a parallel-route evaluator andcomparator, the desired main route can be corrected at any time based onparallel-route calculations. If the navigation system has a display fora road map, then the current (actual) main route can be highlightedaccordingly on a display.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a first block diagram according to the present invention.

FIG. 2 shows a second block diagram according to the present invention.

FIG. 3 shows a function diagram according to the present invention.

FIG. 4 shows a first section of a digital road map according to thepresent invention.

FIG. 5 shows a second section of the digital road map.

FIG. 6 shows a third section of the digital road map.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 depicts a first block diagram of a map-supported navigationsystem, in which a processing unit 1 is connected on the incoming sideto vehicle sensors 3 to record travel direction and trip distance. Alsolinked thereto is a satellite navigation receiver (e.g., GPS receiver)4, likewise for determining vehicle position. Furthermore, processingunit 1 is linked to a readout unit 5, e.g., a display or an acousticaloutput. Furthermore, an input unit 6 and a guidance system 7 are linkedto processing unit 1. Guidance system 7 or satellite receiver 4 areoptionally provided.

FIG. 2 illustrates in detail a second block diagram of the navigationsystem, processing unit 1 being shown with a plurality of functionalblocks. Processing unit 1 contains a composite-navigation dead-reckoningsystem 19, which receives the signals from sensors 3 and/or satellitereceiver 4. From the sensor signals and the previous position,composite-navigation system 19 calculates a new position for thevehicle. The composite-navigation information and the sensor evaluationare transmitted to an error estimator 21, which establishes a range oferror (error span) 25 based on known tolerance errors (FIG. 4). Therange of error 25 is transmitted to a selector 22, which is linked, onthe one hand, to map memory 2. Map memory 2 provides selector 22 withthose streets which come under driving area 24. This driving area 24corresponds then to the main route and to the parallel route area of theroad map (FIG. 4).

Selector 22 is linked to a control computer 20 and relays the main routearea and parallel route area to control computer 20. Furthermore,control computer 20 is connected to composite-navigation system 19 andreceives from it the composite-navigation dead-reckoning data for thevehicle. The control computer initially determines the main routeindependently of the parallel routes. Other possible vehicle positions,besides the main route (parallel routes), are determined here andpursued further on parallel route computers 11, 12. Each parallel routecomputer, in turn, can recognize several plausible vehicle positions andthen start other parallel routes on the parallel route computers. Theparallel route computers are controlled via appropriate control linesSTART. Each parallel route computer is thereby supplied via selector 22with the map detail of driving area 24.

Parallel-route computers 11, 12 are connected to a parallel-routeevaluator and comparator 23. The parallel-route evaluator/comparatorevaluates the parallel routes on the basis of their status information(e.g., conformity of travel direction and street direction). Thoseparallel routes whose plausibility no longer matches that of theparallel routes and the main route are deleted (canceled).

The information pertaining to the absolute vehicle position and theestimated scatter variation range of a satellite-navigation receivingand evaluation device 4 can also cause those parallel routes to becanceled, whose position is no longer situated within the scatter rangeof the satellite-navigation position.

Furthermore, the parallel-route comparator 23 is linked to thecomposite-navigation system 19, which it can supply with correction datafor the vehicle position (route correction).

When a guidance unit 7 is used, it likewise transmits its data to theparallel-route comparator 23, so that in the event of route ambiguity,that route is selected as the main route, which includes one element ofthe route to the target point (destination).

The composite-navigation position can also be corrected directly by thesatellite-receiving and evaluation device 4.

The control computer 20 is linked to an output unit 5, on which, e.g.,given a graphic display, a street detail is shown including the mainroute and a highlighted vehicle. Also possible, however, are directionarrows and travel route and direction recommendations, or an acousticaloutput via guidance unit 7.

Input unit 6 is linked, on the one hand, to processing unit 1 and, onthe other hand, to guidance unit 7, so that, among other things, thedestination entry can be input.

The method according to the present invention is illustrated in FIGS. 3through 6.

FIG. 3 illustrates, e.g., a function diagram for calculating positionand determining the status of a parallel route using parallel-routecomputer 11, 12. It can be assumed, for example, that vehicle position Xis to be calculated on a parallel route 31, which lies within drivingarea 24. In response to starting signal d, parallel-route computer 11,12 extracts from map memory 2 that map section which corresponds todriving area 24 (position a). The route and direction and the drivingdistance of the motor vehicle, which had been determined bycomposite-navigation system 19, are entered at position b. Shouldambiguities with respect to route arise again when this positionaldetermination is made, then another parallel-route computer 11, 12 canbe started at output c. Also determined in addition to position, forexample, is a current status of the conformity between travel directionand street angle. Furthermore, a probability factor for the vehicleposition can be defined in the status information. Also, the statusinformation includes details of the life span of the parallel route.Both the positional determination as well as the status determinationare routed via an output 11 to the parallel-route comparator 23, which,from all existing information and on the basis of plausibility checks,outputs a main route and current (actual) parallel routes. For example,the angle of inclination of a paved road can also be compared with thatof the vehicle, and the main route determined therefrom. If a parallelroute no longer falls under the driving area or no longer conforms withthe compound course, then it can be deleted via an input e. The functiondiagram can be developed as a program for computer 1.

FIG. 4 illustrates a driving area 24, in which passable roads 40 through45 are shown. The assumption is made here that the vehicle is initiallylocated in position X on street 40, which is established momentarily asthe main route. If the vehicle now turns off to the right, then anestimated position X1 results on the basis of the direct feedback andnecessitated by angular and linear errors of the vehicle sensors.Because of the errors, a range of errors 25 is formed around positionX1, as was already formed around position X. The range of errors 25 canvary in magnitude for each calculated position X . . . X4. The magnitudeof the range of errors is determined by the specified tolerances.Therefore, FIG. 4 shows various ranges of errors 25 for the individualpositions X . . . X4. The large, rectangular error field 25 of positionX shifts, for example, along with the new vehicle position X1 andthereby varies its width. This reveals that the actual vehicle positionlies within this field. It is, therefore, assumed that a new position(designated position) X2 is on street 43, which is the next one tofollow the calculated position X1.

Now, on the basis of the turn-off angle of the vehicle in comparison toall roads which have formed a similar angle with the main route 40existing until now, the control computer 20 determines the possiblepositions X2, X3 and X4 on parallel routes 42, 43 and 44, along with thecorresponding new ranges of error 25. Roads 42, 43, 44 are situatedwithin the range of errors of route position X1. Road 41 forms aturn-off angle in the opposite direction and, therefore, is no longer afactor in determining position. The described method, in whichparallel-route positions (here X2, X3 and X4 and roads 44, 43 and 42)proceed from the range of errors 25 of the main route, can equally beapplied by producing parallel routes from the range of errors 25 of aparallel route. The range of error 25 includes the travel-directionmeasuring error and a one-dimensional temporary stop area (possiblelinear error) or a two-dimensional temporary stop area (transverse andlongitudinal error of the assumed position). Based on plausibilityconsiderations, from positions X1 through X4, position X2 with the newerror field 25 is selected as the new designated position on the newlyselected main route (designated road) for which the vehicle position ismost probable. Positions X3, X4 on parallel routes 42, 44 are calculatedfurther and considered again when the next selection is made. Should oneof the parallel routes 42 or 44 be possible as the main route when oneof the next positional determinations is made, then one of the twoparallel routes would be defined as a new main route. In borderlinecases, to prevent a vehicle position X2 from jumping back and forthfrequently, a hysteresis is provided as a function of time or distancefor assessment purposes, so that a determination of a parallel route asa new main route is not changed until on the basis of a few measuringcycles or of a specific total trip distance.

It can also be inferred from FIG. 4 that when there is a turn off intothe new main route 43, the turn-off point at crossing 43, 40 can be usedas the defined correlation point for the length measurement.Alternatively, the difference X1-X2 can be used for the linearcorrection. The method for determining parallel-route positions X3 andX4 is to be carried out accordingly.

Similarly to the linear correction shown in FIG. 4, a positionalcorrection can be performed as shown in FIG. 5. As an example, thevehicle is situated on the main route 50 in position X. The assumptionis now made that the main route 50 divides at a fork into two parallelroutes 51, 52. Because of the composite-navigation process, the vehiclewould be situated at a certain instant in estimated position X5. Sinceposition X5 is not a location on a street, possible positions X8 onparallel route 51 or X7 on parallel route 52 are acceptable. Given arepeated positional determination, also on the basis of the recommendedroute for the destination, a probability results for position X7 as thedesignated position on parallel route 52, which is now pursued furtheras the main route. Parallel route 51 continues to be relevant andcontinues to be calculated using the parallel-route computer 11, 12. Onthe basis of the change of angle from position X5 to X7, a correctionvalue results for the determination of direction, which the continuedcomposite-navigation process can be based on.

FIG. 6 shows a third section of a road map of a navigation system, inwhich case a satellite-navigation receiver 4 (e.g., GPS) is used forcorrecting composite-navigation. The satellite-navigation receiverdetermines its position from the location of several navigationsatellites. This positional determination is likewise afflicted with acertain error. This error is compensated similarly to the examples ofFIG. 4 or 5. Road sections/parallel routes 61 through 68 are shown inerror field 24 of FIG. 6. For example, if as a possible location for thevehicle, GPS receiver 4 determines estimated position X8, then viewed inthe travel direction D, possible position X9 is additionally calculatedon parallel route 61 and possible position X10 on parallel route 63.However, possible positions X13 on 66, X14 on 67, and X12 on 68 can alsobe calculated. A position of the motor vehicle on parallel routes 64 or65 is unlikely for plausibility reasons and is, therefore, eliminated. Arecalculation is then performed to attain the greatest probability, forexample, for a position X11 on parallel route 62, which now become thedesignated position and the main route (designated road), respectively.It is now assumed that the motor vehicle is at position X11, and thisposition is output, for example, on a display 5. Positions X9, X10, X12,X13, X14 on original streets 61, 63, 68, 66, 67 are pursued further forcontrolling the main route 62. However, they are not shown on display 5.

If the navigational system is coupled, for example, to a guidance device7, then, after entering a target destination via input 6 of processingunit 1, a specific target route is selected. The target route is now soplaced that it is calculated with the new main route 62 as the startingposition.

The individual subassemblies of the navigation system or of theprocessing unit 1, such as the composite-navigation system 19, errorestimator 21, selector 22, parallel-route computer 11, 12, orparallel-route comparator 23 are built using conventional modules, suchas amplifiers, comparators, or logic modules. These are known to oneskilled in the art from conventional navigational systems and,therefore, do not need to be elucidated further. In place of individualmodules, it is also possible to provide one or more microcomputers,which are controlled by a corresponding control program.

What is claimed is:
 1. A method for correcting a map-supportednavigation system, comprising the steps of:determining on a map storedin a map memory an estimated position of a vehicle using a compositenavigation arrangement; determining a first error range for theestimated position; determining roads on the map that are substantiallyparallel to a vehicle direction; determining a possible position of thevehicle on each road of the roads, each possible position being withinthe first error range; determining concurrently a second error range foreach possible position, the second error range being variable; selectinga designated road from a set including the roads, the designated roadbeing selected by determining a likelihood that the designated roadrepresents an actual road on which the vehicle is traveling; andselecting the possible position on the selected road as a designatedposition.
 2. The method according to claim 1, further comprising thestep of:receiving a navigation signal from at least one of a vehiclesensor and a navigation device.
 3. The method according to claim 2,further comprising the step of:forming a driving area as a function ofthe navigation signal.
 4. The method according to claim 1, wherein thefirst error range and the second error range include at least one of aone-dimensional area and a two-dimensional area for at least one of alinear error range, a transverse error range and a directional errorrange.
 5. The method according to claim 4, further comprising the stepof:correcting the linear error range of the composite navigationarrangement as a function of a difference between the estimated positionand the designated position.
 6. The method according to claim 1, furthercomprising the step of:extracting the map from the map memory.
 7. Themethod according to claim 1, further comprising the step of:afterselecting the designated position, evaluating each possible position,while plausible, as a potential subsequently designated position.
 8. Themethod according to claim 1, further comprising the step of:afterselecting the designated road, evaluating each road, while plausible, ofthe roads as a potential subsequently designated road.
 9. The methodaccording to claim 8, further comprising the step of:determiningsubstantially parallel roads, where present, for each one of thopotential subsequently designated roads.
 10. The method according toclaim 1, wherein the designated position is output on a road mapdisplay.
 11. The method according to claim 1, further comprising thestep of:extending along one of the roads, the extended road maintaininginitially information about the roads.
 12. The method according to claim1, wherein the step of selecting the designated road includes the stepof comparing a first set of parameters of each of the roads with asecond set of parameters including parameters ascertained from anavigational signal from at least one of a vehicle sensor and anavigation device.
 13. The method according to claim 1, wherein the stepof selecting the designated road includes the step of comparing a firstset of parameters of each of the roads with a second set of parametersincluding at least one of an angle of inclination of the vehicle, actualslope of a road on which the vehicle travels and a length of timeinterval in which one of the roads has been plausible.
 14. The methodaccording to claim 1, wherein the step of selecting the designated roadincludes the step of using a hysteresis characteristic through which achange in a status of a previous designated road is delayed.
 15. Themethod according to claim 1, further comprising the step of:calculatinga difference between the estimated position and the designated positionsubsequent to the vehicle rounding a curve of the designated road. 16.The method according to claim 1, further comprising the stepof:repositioning the estimated position of the vehicle using the datafrom a navigation-satellite receiver.
 17. The method according to claim16, wherein a particular road of the roads is not plausible if theparticular road is entirely outside an error range of thenavigation-satellite receiver.
 18. The method according to claim 1,further comprising the step of:using a guidance system, wherein, when anambiguity occurs in selecting the designated road, conformity with atarget route as determined by the guidance system is considered.
 19. Amethod for correcting a map-supported navigation system, comprising thesteps of:determining on a map stored in a map memory an estimatedposition of a vehicle using a composite navigation arrangement;determining a first error range for the estimated position; determiningroads on the map that are substantially parallel to a vehicle direction;determining a possible position of the vehicle on each road of theroads, each possible position being within the first error range;determining concurrently a second error range for each possibleposition, the second error range being variable; selecting a designatedroad from a set including the roads, the designated road being selectedby determining a likelihood that the designated road represents anactual road on which the vehicle is traveling; and selecting thepossible position on the selected road as a designated position, whereinthe second error range is predetermined for each possible position, thesecond error range having a magnitude determined by at least one of ameasuring tolerance of a vehicle sensor and a measuring tolerance of anavigation device, the second error range including one of aone-dimensional area and a two dimensional area, at least one of theone-dimensional area and the two-dimensional area being provided for atleast one of a linear error, a transverse error and a directional error.20. The method according to claim 19, wherein the second error range isa same size for all of the roads, the second error range beingprescribed by tolerances of the sensor and tolerances of the navigationdevice.
 21. The method according to claim 19, wherein the second errorrange is calculated for each of the roads.
 22. The method according toclaim 19, wherein each of the roads is associated with a respectiveerror range, a size of the respective error range being determined byrespective prescribed tolerances of the sensor.
 23. A map-supportednavigation system, comprising:a processing unit including a selectordevice and at least one computer for calculating parameters for roadsthat are substantially parallel to a vehicle direction; sensors coupledto the processing unit and providing navigational signals, the sensorsascertaining at least one of a vehicle direction and a distance traveledby the vehicle; a map memory coupled to the processing unit, the mapmemory providing data with respect to the roads; an input unit coupledto the processing unit; and an output unit coupled between theprocessing unit and the map memory, the output unit outputting adesignated position of the vehicle, wherein the selector device accessesdata with respect to the roads including data concerning an error rangeassociated with each possible position on each of the roads, theselector device selecting a designated road by determining a likelihoodthat the designated road represents a road on which the vehicle isactually traveling, the error range including at least one of aone-dimensional area and a two-dimensional area for at least one of alinear error range, a transverse error range and a directional errorrange, the error range being determined concurrently for each possibleposition and being variable, and wherein the processing unit correctsthe linear error range of a composite navigation arrangement as afunction of a difference between an estimated position and thedesignated position, the estimated position determined using thecomposite navigation arrangement.
 24. The map-supported navigationsystem according to claim 23, further comprising:a guidance unit coupledto the processing unit, to the output unit end to the input unit, theguidance unit assisting in selecting the designated road.
 25. Themap-supported navigation system according to claim 23, wherein thedesignated position is visually displayed on the output unit.
 26. Themap-supported navigation system according to claim 23, wherein theoutput unit displays the designated position on the designated road. 27.The map-supported navigation system according to claim 23, furthercomprising:a guidance unit coupled to the processing unit and to theinput unit, the guidance unit generating a guidance starting positionafter entering a target destination via an input unit.
 28. Themap-supported navigation system according to claim 23, furthercomprising:a navigation-satellite receiver coupled to the processingunit, the navigation-satellite receiver using the received data toreposition the estimated position of the vehicle.